Nissan has resumed domestic car production in Japan after being suspended, following the scandal of uncertified technicians signing off on final inspections.
The automaker stated a third-party investigation also revealed that inspection staff had not been properly trained, according to a Reuters report.
The investigation found the manufacturer had shared test questions with examinees and failed to teach trainees for the correct number of hours.
Nissan has now stated it will retrain and retest inspectors while updating inconsistencies between plant operating manuals and plant activities.
The scandal has caused a recall of 1.2 million vehicles for re-inspection, including all passenger cars it produced for sale in Japan over the past three years.